Method for the continuous casting of metal ingots or strips

ABSTRACT

A method for the continuous casting of metal ingots or strips comprises the steps of continuously supplying molten metal to a relatively short mold, continuously applying a liquid coolant to the outer surface of the mold to form an outer shell of solidified metal within the mold, withdrawing the solidified metal in the form of an ingot or strip from the bottom of the mold at a predetermined casting speed, continuously applying a liquid coolant to the surface of the ingot or strip emerging from the mold to cool the ingot or strip, and effectively removing substantially all of the liquid coolant from the surface of the ingot or strip at a distance from the bottom of the mold which is greater than 0.5 times the minimum transverse dimension of the ingot or strip.

United States Patent Gervais et al.

METHOD FOR THE CONTINUOUS CASTING OF METAL INGOTS OR STRIPS Assignee:

Inventors: Edouard Gervais, Montreal; Henri Levert, Lachine; Pierre Chollet, Pierrefonds, all of Canada Noranda Mines Limited, Toronto,

Canada June 13, 1973 U.S. Cl 164/89; 164/283 8 Int. Cl B22d 11/12 Field of Search 164/89, 283 S References Cited U NITED STATES PATENTS Zeigler 164/89 Zeigler 164/89 Kilpatrick 164/283 S Elliott et al l64/283 S X Gervais et al 164/82 X June 24, 1975 Primary Examiner-Robert D. Baldwin Assistant Examiner.lohn E. Roethel Attorney, Agent, or F irm--Cooper, Dunham, Clark, Griffin and Moran [57] ABSTRACT A method for the continuous casting of metal ingots or strips comprises the steps of continuously supplying molten metal to a relatively short mold, continuously applying a liquid coolant to the outer surface of the mold to form an outer shell of solidified metal within the mold, withdrawing the solidified metal in the form of an ingot or strip from the bottom of the mold at a predetermined casting speed, continuously applying a liquid coolant to the surface of the ingot or strip emerging from the mold to cool the ingot or strip, and effectively removing substantially all of the liquid coolant from the surface of the ingot or strip at a distance from the bottom of the mold which is greater than 0.5 times the minimum transverse dimension of the ingot or strip.

12 Claims, 2 Drawing Figures 9L nu PATENTEDJUN 24 ms SHEET I" I 8 9 1 O 4 J I UN I975 SHEET 2 STRIPPER DISTANCE (INCHES) a FIG. 2

METHOD FOR THE CONTINUOUS CASTING OF METAL INGOTS OR STRIPS FIELD OF THE INVENTION This invention relates to the continuous casting of castable metal ingots or strips, and more particularly to the casting of zinc-aluminum alloys and of commercial pure aluminum.

Canadian Pat. No. 528,229 discloses a method for casting aluminum and aluminum alloys wherein molten metal is continuously supplied to a short open mold which is cooled by applying a liquid coolant to the outer surface of the mold so as to form an outer shell of solidified metal within the mold. The ingot is withdrawn from the bottom of the mold while a liquid cool ant is continuously applied to the surface of the casting so as to cause a relatively rapid freezing of the molten metal and avoidance of a deep molten crater which causes shrinkage porosity. A so-called wiper is located at a certain distance from the bottom of the mold to stop the cooling action and avoid the excessive internal stresses generated by overcooling and resulting in center splits and cracks in the ingot.

Water wiping leads to a reduction of the cooling rate in the center of the casting, as well as providing a means to minimize the differential thermal contraction between the center of the casting and layers closer to the surface. The differential thermal contraction of various layers of a casting is well recognized as being the major cause of crack formation in the center of the casting as well as complete casting splitting. The differential thermal contraction originates from the thermal gradient existing during solidification and cooling.

The above patent discloses that the level of coolant removal below the bottom of the mold should be located within a range of from A; to V; times the minimum transverse dimension of the particular ingot being cast. With billets varying from 3 to 8 inches in diameter, the lowest distance of water removal below the mold bottom would vary between 1.5 to 4 inches and, with a wiper located at such a small distance from the mold bottom, only slow casting speeds can be obtained. Indeed, in the examples given in the above patent, casting speeds varying from /8 to 3 inches/minute are disclosed.

SUMMARY OF THE INVENTION 1t is therefore the object of the present invention to increase the speed at which metal ingots or strips, and more particularly zinc-aluminum alloys and commercial aluminum can be cast.

Generally speaking, relatively high casting speeds have been obtained by effectively removing the liquid coolant from the surface of the ingot or strip at a distance from the bottom of the mold which is greater than 0.5 times the minimum transverse dimension of the ingot or strip. The position of the water removal device hereafter called stripper depends on such factors as alloy composition, cast product dimensions, casting speed, mold length and design, water flow rate and velocity and finally the molten metal feeding arrangement and its effect on turbulence and temperature distribution within the liquid metal crater of the casting.

For a given experimental setup, it has been found that the casting speed depends on the position of water stripping. In fact, during casting of 8 inch diameter billets containing 25% Al, Cu and 0.05% Mg, the balance being zinc with incidental impurities, it has been found that the casting speed at which sound billets we re produced was proportional to the distance of cooling liquid removal from the mold. Sound billets were cast 5 at speeds varying from 7 to 20 in/min at distances of liquid removal varying from 6 to 22 inches from the bottom of the mold. A 5 inch diameter sound billet of the same composition has also been produced at a speed of 12 in/min when the stripper was located between 3% and 5% inch from the mold bottom. Billets of 3% and 4 inch diameter have also been successfully produced at relatively high speeds with s stripper located about 1.5 to 1.8 times the diameter of the billet.

Various 3% inch diameter billets of zinc-aluminum alloys containing from -26% aluminum, from 1-1 0% copper, and from 0.013 to 0.12% magnesium have been cast. Sound billets showing no sign of shrinkage porosity and no cracks were obtained at a casting speed of 8 in/min and using a stripper located at 6 inches from the mold bottom. In this case, the distance from the bottom of the mold was about twice the diameter of the billet. However, more concern was placed on the production of sound billets than on the optimization of the casting process. Consequently, higher casting speeds could have been obtained by placing the stripper at a greater distance from the bottom of the mold.

It has also been possible to cast a 3% inch diameter billet of the following composition: zinc, 33% aluminum, 5.2% copper, 0.057% magnesium which is more crack prone than the above mentioned alloys. The above billet was cast at a speed of 3 in/min combined with water stripping at about 4 inches from the mold. Again, higher casting speeds could most probably be obtained but were not investigated. The distance of the stripper from the bottom of the mold is, in this present case, about 1.2 times the diameter of the billet.

It has also been possible to cast sound strips of a zincaluminum alloy containing 25% aluminum, 5% copper, and 0.05% magnesium. The strip was 0.7 inch thick and 6 inch wide and was cast at a speed of 1 l inch/min with a stripper located 0.5 inch below the bottom of the mold. The same experiment was also made with a zincaluminum alloy containing 22% aluminum, 1% copper, and 0.05% magnesium. Even in these two cases, the distance of the stripper if 0.7 times the minimum transverse dimension of the strip, which is higher than the distance mentioned in the above-identified patent.

A strip of an alloy containing 22% aluminum, 1% copper and the balance zinc with incidental impurities, measuring 14 inches wide by 0.5 inch thick was cast without cracking at about 15 in/min with a stripper located at 0.5 inch below the mold exit. In this case the distance of the stripper is 1 times the minimum transverse dimension of the strip.

A strip of an alloy containing 22% aluminum, 1% copper and 0.05% magnesium, the balance being zinc with incidental impurities, having the same dimension as above, was cast without cracking at about 22 in/min with a stripper located at 0.5 inch below the mold exit.

Commercial pure aluminum billets have also been cast following the above technique. The billets had a diameter of 8 inches and were cast at a speed of 17 in/- min with a stripper located at 24 inches below the mold. 1n this case, the distance of the stripper was 3 times the diameter of the billet.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be disclosed, by way of exanb ple, with reference to the accompanying drawings in which:

FIG. I illustrates a schematical longitudinal, partially sectional view of a mold arrangement that may be used for carrying the method in accordance with the invention, and

FIG. 2 illustrates a graph showing the relationship between stripper distance from the bottom of the mold and the casting speed in the mold according to the present invention.

DETAILED DESCRIPTION FIG. 1 illustrates, schematically, an apparatus for casting metals such as zinc-aluminum alloys or commercially pure aluminum. As shown in this figure, molten metal M is introduced into an open top mold 10 and cooling water W into a jacket 11 surrounding such mold. Due to the cooling action of this water, the metal commences to solidify at a point 12 within the mold starting at the edges and continuing as shown by line 13 to a point 14 where the entire billet becomes a solid substance 5. The cooling of the billet coming out of the mold I is stopped by using a water stripper 15 at a level above the full solidification point 14. Thus, cooling water which falls down from the jacket 1] onto the surface of the billet which comes out from mold is stripped off by stripper which thereby arrests the cooling action at that level before the solidification of the billet is complete.

The mold arrangement shown in FIG. 1 is, however, not limitative and other suitable arrangements may be used although there must be a provision to arrest the cooling of the billet. For example, a jet of compressed air could be used in place ofstripper 15. In the arrange ment shown in FIG. 1, there is also illustrated a closure 16 for the mold having an opening 17 for the introduc tion of the molten metal. The closure may be suitably bolted to separate the different compartments within the jacketed mold and also for support on a suitable platform (not shown) or the like.

The cooling water falls down from the jacket 11 which is open at its bottom and cools the billet for a relatively short period of time after it has emerged from the mold and then this cooling water is removed by a stripping device 15 which may be made of any suitable material such as hard rubber and suitably attached by an annular supporting means 18 the height of which with respect to the mold is adjustable. This permits to control the distance of the stripper from the mold in a desired manner.

It has been found that the further away the stripper is located from the bottom of the mold, the faster the casting speed. However, the casting speed which depends on the position of the stripper is in turn a func tion of factors such as metal composition and dimen sions of the casting.

The following examples will illustrate the various casting speeds obtained in accordance with the method of the present invention:

EXAMPLE 1 A systematic investigation of the relationship between casting speed and stripper location was carried out on 8 inch diameter billets of the following composition: 25% aluminum, 5% copper, 0.05% magnesium, the balance being zinc with incidental impurities. FIG. 2 shows the recommended stripper location as a func tion of casting speed. As shown, casting speeds up to 20 in/min can be easily obtained with stripper location up to 22 inches from the mold bottom. The stripper loca tion from the bottom of the mold is up to 3 times the diameter of the billet, which is much higher than the maximum distance of /z the diameter of the billet disclosed in the above patent.

As part of the investigation, the sump profile and bi]- let isotherm were determined by means of thermocoupies positioned in the solidifying billets. The casting conditions were as follows:

a) casting speed 8 in/min bl stripper location 7 inch below mold bottom c) metal casting temperature 550C dl water flow rate 55 gal/min The results have shown that:

a. The skin thickness at the point of stripping was l.75 inch for the solidus and 2.1 inch for the liquidus; the minimum skin thickness to avoid billet remelting is estimated to be l.2 inch. Hence at the point of strip ping, about 68% of the billet is solid whereas about 10% is mushy and about 22% is still liquid.

b. The billet center passes through the liquidus tem perature (447C) at about 19 inches from the mold exit whereas it is completely solid (solidus 400C) at about 25 inches from the mold.

c. About 4 minutes after a given cross-sectional plane of the billet has emerged from the mold (32 inches) it is at a uniform temperature (350C), except for approximately the First k inch from the surface.

It will be appreciated that, in this example, the production of a crack free casting does not depend on the molten metal crater depth but rather on the skin thickness at the point of stripping since the location of the water stripping devices is related to the time the emerg ing billet is in contact with water.

The above results are only applicable to the disclosed experimental casting conditions; it is expected that the best stripper location will vary with casting conditions such as: mold length and design, water flow rate and velocities, the liquid metal turbulence in the billet crater, and with the temperature distribution within the liquid metal in the crater.

EXAMPLE 2 Crack free, 5 inch diameter billets of the same alloy composition as the one disclosed above have been produced satisfactorily at a speed of l2 in/min when the stripper was located between 3% to 5% inch from the mold. The metal temperature was 550C and a water flow rate of 20 gal/min was used for cooling. The recommended stripper location is 4% inch, so that varia tions of the casting conditions such as the following would not lead to the production of cracked or porous billets:

a. variation in the mold heat transfer properties b. liquid metal temperature fluctuation c. fluctuation of the water flow rate and temperature d. slight changes in the molten metal feeding systems.

Billets of 3% and 4 inch diameter have also been successfully produced at relatively high speed with a stripper located about L5 to 1.8 times the diameter of the billet from the bottom of the mold.

lt has also been found that the skin thickness relation mentioned above when casting 8 inch diameter billets does not apply to other diameters since the thermal gradient and therefore the differential contraction between the center and the outer layers of the billet is different. In fact, from some experiments carried out with 4 inch diameter billets, it is apparent that in order to produce crack free billets, the stripper only needed to be located at a level close to the bottom of the metal crater.

EXAMPLE 3 A number of 3% inch diameter zinc-aluminum billets of the composition given in the following Table l were cast:

TABLE 1 Alloy Composition Zinc-Aluminum The above alloys were cast at a speed of 8 in/min with a stripper located at 6 inches from the mold bottom. The water flow rate in the jacket surrounding the mold was about 9 gal/min. During these experiments, the production of sound billets was considered more important than the optimization of the casting process. Consequently, it would certainly have been possible to obtain higher casting speeds by positioning the stripper further away from the bottom of the mold. The above Table I thus shows that zinc base alloys ranging from to 26% aluminum, with copper levels from I to l0% and magnesium levels from 0.013 to O.l2% with incidental impurities can be successfully cast using a water stripper located at a distance which is almost twice the diameter of the billet from the bottom of the mold. This is therefore much higher than the maximum of 0.5 times the maximum transverse dimension of the casting suggested in the above-mentioned patent.

EXAMPLE 4 A 3% inch diameter billet of the following composition: 33% aluminum, 5.2% copper, 0.057 magnesium, the remainder being zinc with incidental impurities, was successfully cast at a speed of 3 in/min combined with water stripping at about 4 inches from the mold bottom. A sound billet was obtained although it is known that this alloy is particularly crack prone. Here again no special effort was made to optimize the casting process and higher casting speeds could most probably be obtained by placing the stripper at a larger distance from the bottom of the mold.

EXAMPLE 5 The technique developed to produce crack free billets has also been successfully used to produce 0.7 inch thick by 6 inches wide strips of the following composition:

a. 25% aluminum, 5% copper, 0.05% magnesium, balance zinc with incidental impurities,

b. 22% aluminum, 1% copper, 0.05% magnesium, balance zinc with incidental impurities.

The casting speed was 1 l in/min and the point of liquid removal located 0.5 inch below the mold bottom. The casting temperature was 525C and the cooling water flow rate 10 gal/min. Without water stripping it was impossible to produce a crack free strip even at a casting speed of 4 in/min.

Even with strips it will be noted that the distance of coolant removal is higher than 0.5 times the minimum transverse dimension of the casting as mentioned in the above patent: in the present case the distance of coolant removal is 0.7 times the minimum dimension (0.7 in) of the strip.

EXAMPLE 6 A strip of 22% aluminum, 1% copper, the balance zine with incidental impurities, measuring 14 inches wide by 0.5 inch thick was cast without cracking under the following experimental conditions:

Metal temperature 545C Casting speed [5 V4 in/min Point of stripping 0.5 inch below the mold exit Water flow rate It) gal/min A strip cast under identical conditions but without stripping was cracked in the center of the width along the casting direction.

EXAMPLE 7 22 in/min 0.5 inch below the mold exit about 10 gal/min Metal temperature Casting speed Point of stripping Water flow rate A strip of this alloy cast under identical condition as in example 6 above cracked during the casting operation. An attempt was made to produce a crack free strip at 12 and I9 in/min with the stripper located at 0.5 from the mold; the strip cracked during the casting operation. This shows that the alloy used for this example is more crack prone than the alloy of example 6.

EXAMPLE 8 Casting of commercial purity aluminum billets (99.5% aluminum) having a diameter of 8 inch was also successfully done at a speed of I? in/min with a stripper located at 24 inches below the mold. in this case, the distance of coolant removal was also much higher than the above patent (3 times the diameter of the billet).

The above examples show that crack free ingots or strips can be cast at relatively high speeds by placing the stripper at a predetermined location from the mold bottom which will be higher than 0.5 times the minimum transverse dimension of the ingot or strip. This permits to cast at much higher speed than with the prior art techniques.

It has also been noted that casting at relatively high speed leads to the production of ingots or strips which have an excellent surface finish which may eliminate the need of surface preparation in view of further pro cessing.

What is claimed is:

l. A method for the continuous casting of zincaluminum billets of about inches in diameter at relatively high speed comprising the steps of:

a. continuously supplying a molten zinc-aluminum alloy containing about 25% aluminum, 5% copper, 0.05% magnesium, the balance being zinc with incidental impurities, to a relatively short mold;

b. continuously applying a liquid coolant to the outer surface of the mold to form an outer shell of solidified meta] within the mold;

c. withdrawing the solidified metal in the form of a billet from the bottom of the mold at a casting speed of about 12 in/min;

d. continuously applying a liquid coolant to the surface of the billet emerging from the mold to cool the billet; and

e. effectively removing all of the liquid coolant from the surface of the billet at a distance from the bottom of the mold which varies between 3% and 5% inches.

2. A method as defined in claim 1, wherein said distance of liquid coolant removal is 4% inches from the mold.

3. A method for the continuous casting of zincaluminum billets of about 3% inches in diameter at relatively high speed comprising the steps of:

a. continuously supplying a molten zinc-aluminum alloy containing from -26% aluminum, from 1 to |0% copper, from 0.0l3 to 0.l2% magnesium, the balance being zinc with incidental impurities, to a relatively short mold;

b. continuously applying a liquid coolant to the outer surface of the mold to form an outer shell of solidifled metal within the mold;

c. withdrawing the solidified metal in the form of a billet from the bottom of the mold at a casting speed which is about 8 inlmin;

d. continuously applying a liquid coolant to the surface of the billet emerging from the mold to cool the billet; and

e. effectively removing all of the liquid coolant from the surface of the billet at a distance from the bottom of the mold which is about 6 inches.

4. A method for the continuous casting of zincaluminum billets of about 3% inch in diameter at rela tively high speed comprising the steps of:

a. continuously supplying a molten zinc-aluminum alloy containing about 33% aluminum, 5.2% copper, 0.05 7% magnesium. the balance being zinc with incidental impurities, to a relatively short mold;

b. continuously applying a liquid coolant to the outer surface of the mold to form an outer shell of solidilied metal within the mold;

c. withdrawing the solidified metal in the form of a billet from the bottom of said mold at a casting speed which is about 3 in/min;

d. continuously applying a liquid coolant to the surface of the billet emerging from the mold to cool the billet; and

e. effectively removing all of the liquid coolant from 5 the surface of the billet at a distance from the bottom of the mold which is about 4 inches.

5. A method for the continuous casting of zincaluminum strips having a thickness of about 0.7 inch and a width of about 6 inches at relatively high speed comprising the steps of a. continuously supplying a molten zinc-aluminum alloy containing about aluminum, 5% copper, 0.05% magnesium, the balance being zinc with incidental impurities, to a relatively short mold;

b. continuously applying a liquid coolant to the outer surface of the mold to form an outer shell of solidifled metal within the mold;

c, withdrawing the solidified metal in the form of a strip from the bottom of said mold at a casting speed which is about 1 l in/min;

d. continuously applying a liquid coolant to the outer surface of the strip emerging from the mold to cool the strip; and

c. effectively removing all of the liquid coolant from the surface of the strip at a distance from the bottom of the mold which is about 0.5 inch.

6. A method for the continuous casting of zincaluminum strips having a thickness of about 0.7 inch and a width of about 6 inches at relatively high speed comprising the steps of:

a. continuously supplying a molten zinc-aluminum alloy containing about 22% aluminum 1% copper, 0.05% magnesium, the balance being zinc with incidental impurities, to a relatively short mold;

b. continuously applying a liquid coolant to the outer surface of the mold to form an outer shell of solidified metal within the mold;

c. withdrawing the solidified metal in the form of a strip from the bottom of said mold at a casting speed of about i l in/min;

d. continuously applying a liquid coolant to the surface of the strip emerging from the mold to cool the strip; and

e. effectively removing all of the liquid coolant from the surface of the strip at a distance from the bottom of the mold which is about 0.5 inch.

7. A method for the continuous casting of zincaluminum strips having a thickness of about 0.5 inch and a width of about 14 inches at relatively high speed comprising the steps of:

a. continuously supplying a molten zinc-aluminum alloy containing about 22% aluminum, 1% copper, 0.05% magnesium, the balance being zinc with incidental impuritites, to a relatively short mold;

b. continuously applying a liquid coolant to the outer surface of the mold to form an outer shell of solidified metal within the mold;

c, withdrawing the solidified metal in the form of a strip from the bottom ofthe mold at a casting speed of about 22 in/min;

d. continuously applying a liquid coolant to the surface of the strip emerging from the mold to cool the strip; and

e. effectively removing all of the liquid coolant from the surface of the strip at a distance from the bottom of the mold which is about 0.5 inch.

8. A method for the continuous casting of zinc aluminum strips having a thickness of about 0.5 inch and a width of about 14 inches at relatively high speed comprising the steps of:

a. continuously supplying a molten zinc-aluminum alloy containing about 22% aluminum, l% copper, the balance being zinc with incidental impurities, to a relatively short mold;

b. continuously applying a liquid coolant to the outer surface of the mold to form an outer shell of solidifled metal within the mold;

ct withdrawing the solidified metal in the form of a strip from the bottom of the mold at a casting speed of about in/min;

d. continuously applying a liquid coolant to the surface of the strip emerging from the mold to cool the strip; and

e. effectively removing all of the liquid coolant from the surface of the strip at a distance from the bottom of the mold which is about 0.5 inch.

9. A method for the continuous casting of commercially pure aluminum billets of about 8 inches in diameter at relatively high speed comprising the steps of:

a. continuously supplying a molten aluminum containing about 99.5% aluminum to a relatively short mold;

b. continuously applying a liquid coolant to the outer surface of the mold to form an outer shell of solidified metal within the mold;

c. withdrawing the solidified metal in the form of a billet from the bottom of the mold at a casting speed of about [7 in/min;

d. continuously applying the liquid coolant to the surface of the billet emerging from the mold to cool the billet; and

e. effectively removing all of the liquid coolant from the surface of the billet at a distance of about 24 inches from the bottom of the mold.

10. A method for the continuous casting of zincaluminum billets of about 3% to about 8 inches in diameter at relatively high speed comprising the steps of:

a. continuously supplying a molten zinc-aluminum alloy to a relatively short mold;

b. continuously applying a liquid coolant to the outer surface of the mold to form an outer shell of solidified metal within the mold;

c. withdrawing the solidified metal in the form of a billet from the bottom of the mold at a casting speed which is higher than 88 d. continuously applying a liquid coolant to the surface of the billet emerging from the mold to cool the billet; and

e. effectively removing all of the liquid coolant from the surface of the billet at a distance varying between 3% and 7 inches.

11. A method for the continuous casting of zincaluminum strips having a thickness of about 0.5 to about 0.7 inch at relatively high speed comprising the steps of:

a. continuously supplying a molten zinc-aluminum alloy to a relatively short mold;

b. continuously applying a liquid coolant to the outer surface of the mold to form an outer shell of solidified metal within the mold;

c. withdrawing the solidified metal in the form of a strip from the bottom of the mold at a casting speed; varying between about I l to about 22 in/- d. continuously applying the liquid coolant to the surface of the strip emerging from the mold to cool the strips; and

e. effectively removing all of the liquid coolant from the surface of the strip at a distance from the bottom of the mold which is about 0.5 inch.

12. A method for the continuous casting of aluminum billets at relatively high speed comprising the steps of:

a. continuously supplying molten aluminum containing about 99.5% aluminum to a relatively short mold;

b. continuously applying a liquid coolant to the outer surface of the mold to form an outer shell of solidifled metal within the mold;

c. withdrawing the solidified metal in the form of a billet from the bottom of the mold at a predetermined casting speed;

d. continuously applying a liquid coolant to the surface of the billet emerging from the mold to cool the billet; and

e. effectively removing all of the liquid coolant from the surface of the billet at a distance from the bottom of the mold which is about 3 times the diameter of the billet. 

1. A METHOD FOR THE CONTINUOUS CASTING OF ZINC-ALUMINUM BILLETS OF ABOUT 5 INCHES IN DIAMETER AT RELATIVELY HIGH SPEED COMPRISING THE STEPS OF: A. CONTINUOUSLY SUPPLYING A MOLTEN ZINC-ALUMINUM ALLOY CONTAINING ABOUT 25% ALUMINUM, 5% COPPER, 0.05% MAGNESIUM, THE BALANCE BEIN ZINC WITH INCIDENTAL IMPURITIES, TO A RELATIVELY SHORT MOLD; B. CONTINUOUSLY APPLYING A LIQUID COOLANT TO THE OUTER SURFACE OF THE MOLD TO FORM AN OUTER SHELL OF SOLIDIFIED METAL WITHIN THE MOLD; C. WITHDRAWING THE SOLIDIFIED METAL IN THE FORM OF ABILLET FROM THE BOTTOM OF THE MOLD AT A CASTING SPEED OF ABO BILLE 12 IN/MIN; D. CONTINUOUSLY APPLYING A LIQUID COOLANT TO THE SURFACE OF THE BILLET EMERGING FROM THE MOLD TO COOL THE BILLET; AND E. EFFECTIVELY REMOVING ALL OF THE LIQUID COOLANT FROM THE SURFACE OF THE BILLET AT A DISTANCE FROM THE BOTTOM OF THE MOLD WHICH VARIES BETWEEN 3 3/4 AND 5 1/4 INCHES.
 2. A method as defined in claim 1, wherein said distance of liquid coolant removal is 4 3/4 inches from the mold.
 3. A method for the continuous casting of zinc-aluminum billets of about 3 1/4 inches in diameter at relatively high speed comprising the steps of: a. continuously supplying a molten zinc-aluminum alloy containing from 10-26% aluminum, from 1 to 10% copper, from 0.013 to 0.12% magnesium, the balance being zinc with incidental impurities, to a relatively short mold; b. continuously applying a liquid coolant to the outer surface of the mold to form an outer shell of solidified metal within the mold; c. withdrawing the solidified metal in the form of a billet from the bottom of the mold at a casting speed which is about 8 in/min; d. continuously applying a liquid coolant to the surface of the billet emerging from the mold to cool the billet; and e. effectively removing all of the liquid coolant from the surface of the billet at a distance from the bottom of the mold which is about 6 inches.
 4. A method for the continuous casting of zinc-aluminum billets of about 3 1/4 inch in diameter at relatively high speed comprising the steps of: a. continuously supplying a molten zinc-aluminum alloy containing about 33% aluminum, 5.2% copper, 0.057% magnesium, the balance being zinc with incidental impurities, to a relatively short mold; b. continuously applying a liquid coolant to the outer surface of the mold to form an outer shell of solidified metal within the mold; c. withdrawing the solidified metal in the form of a billet from the bottom of said mold at a casting speed which is about 3 in/min; d. continuously applying a liquid coolant to the surface of the billet emerging from the mold to cool the billet; and e. effectively removing all of the liquid coolant from the surface of the billet at a distance from the bottom of the mold which is about 4 inches.
 5. A method for the continuous casting of zinc-aluminum strips having a thickness of about 0.7 inch and a width of about 6 inches at relatively high speed comprising the steps of : a. continuously supplying a molten zinc-aluminum alloy containing about 25% aluminum, 5% copper, 0.05% magnesium, the balance being zinc with incidental impurities, to a relatively short mold; b. continuously applying a liquid coolant to the outer surface of the mold to form an outer shell of solidified metal within the mold; c. withdrawing the solidified metal in the form of a strip from the bottom of said mold at a casting speed which is about 11 in/min; d. continuously applying a liquid coolant to the outer surface of the strip emerging from the mold to cool the strip; and c. effectively removing all of the liquid coolant from the surface of the strip at a distance from the bottom of the mold which is about 0.5 inch.
 6. A method for the continuous casting of zinc-aluminum strips having a thickness of about 0.7 inch and a width of about 6 inches at relatively high speed comprising the steps of: a. continuously supplying a molten zinc-aluminum alloy containing about 22% aluminum 1% copper, 0.05% magnesium, the balance being zinc with incidental impurities, to a relatively short mold; b. continuously applying a liquid coolant to the outer surface of the mold to form an outer shell of solidified metal within the mold; c. withdrawing the solidified metal in the form of a strip from the bottom of said mold at a casting speed of about 11 in/min; d. continuously applying a liquid coolant to the surface of the strip emerging from the mold to cool the strip; and e. effectively removing all of the liquid coolant from the surface of the strip at a distance from the bottom of the mold which is about 0.5 inch.
 7. A method for the continuous casting of zinc-aluminum strips having a thickness of about 0.5 inch and a width of about 14 inches at relatively high speed comprising the steps of: a. continuously supplying a molten zinc-aluminum alloy containing about 22% aluminum, 1% copper, 0.05% magnesium, the balance being zinc with incidental impuritites, to a relatively short mold; b. continuously applying a liquid coolant to the outer surface of the mold to form an outer shell of solidified metal within the mold; c. withdrawing the solidified metal in the form of a strip from the bottom of the mold at a casting speed of about 22 in/min; d. continuously applying a liquid coolant to the surface of the strip emerging from the mold to cool the strip; and e. effectively removing all of the liquid coolant from the surface of the strip at a distance from the bottom of the mold which is about 0.5 inch.
 8. A method for the continuous casting of zinc-aluminum strips having a thickness of about 0.5 inch and a width of about 14 inches at relatively high speed comprising the steps of: a. continuously supplying a molten zinc-aluminum alloy containing about 22% aluminum, 1% copper, the balance being zinc with incidental impurities, to a relatively short mold; b. continuously applying a liquid coolant to the outer surface of the mold to form an outer shell of solidified metal within the mold; c. withdrawing the solidified metal in the form of a strip from the bottom of the mold at a casting speed of about 15 1/4 in/miN; d. continuously applying a liquid coolant to the surface of the strip emerging from the mold to cool the strip; and e. effectively removing all of the liquid coolant from the surface of the strip at a distance from the bottom of the mold which is about 0.5 inch.
 9. A method for the continuous casting of commercially pure aluminum billets of about 8 inches in diameter at relatively high speed comprising the steps of: a. continuously supplying a molten aluminum containing about 99.5% aluminum to a relatively short mold; b. continuously applying a liquid coolant to the outer surface of the mold to form an outer shell of solidified metal within the mold; c. withdrawing the solidified metal in the form of a billet from the bottom of the mold at a casting speed of about 17 in/min; d. continuously applying the liquid coolant to the surface of the billet emerging from the mold to cool the billet; and e. effectively removing all of the liquid coolant from the surface of the billet at a distance of about 24 inches from the bottom of the mold.
 10. A method for the continuous casting of zinc-aluminum billets of about 3 1/4 to about 8 inches in diameter at relatively high speed comprising the steps of: a. continuously supplying a molten zinc-aluminum alloy to a relatively short mold; b. continuously applying a liquid coolant to the outer surface of the mold to form an outer shell of solidified metal within the mold; c. withdrawing the solidified metal in the form of a billet from the bottom of the mold at a casting speed which is higher than 88 d. continuously applying a liquid coolant to the surface of the billet emerging from the mold to cool the billet; and e. effectively removing all of the liquid coolant from the surface of the billet at a distance varying between 3 3/4 and 7 inches.
 11. A method for the continuous casting of zinc-aluminum strips having a thickness of about 0.5 to about 0.7 inch at relatively high speed comprising the steps of: a. continuously supplying a molten zinc-aluminum alloy to a relatively short mold; b. continuously applying a liquid coolant to the outer surface of the mold to form an outer shell of solidified metal within the mold; c. withdrawing the solidified metal in the form of a strip from the bottom of the mold at a casting speed; varying between about 11 to about 22 in/min; d. continuously applying the liquid coolant to the surface of the strip emerging from the mold to cool the strips; and e. effectively removing all of the liquid coolant from the surface of the strip at a distance from the bottom of the mold which is about 0.5 inch.
 12. A method for the continuous casting of aluminum billets at relatively high speed comprising the steps of: a. continuously supplying molten aluminum containing about 99.5% aluminum to a relatively short mold; b. continuously applying a liquid coolant to the outer surface of the mold to form an outer shell of solidified metal within the mold; c. withdrawing the solidified metal in the form of a billet from the bottom of the mold at a predetermined casting speed; d. continuously applying a liquid coolant to the surface of the billet emerging from the mold to cool the billet; and e. effectively removing all of the liquid coolant from the surface of the billet at a distance from the bottom of the mold which is about 3 times the diameter of the billet. 